this.Base64 = function (str) {

            return btoa(encodeURIComponent(str).replace(/%([0-9A-F]{2})/g, function (match, p1) {

                return String.fromCharCode('0x' + p1);

            }));

        }

        public static string UnBase64String(string value)

        {

            if (value == null || value == "")

            {

                return "";

            }

            byte[] bytes = Convert.FromBase64String(value);

            return Encoding.UTF8.GetString(bytes);

        }